Dear Prof. Goncalo,

Please try the software SocioGram. It is a free software which can be downloaded from the following link. Hope that it is suitable for your requirement.

Regards,

Sudev

http://sociogram.software.informer.com/

The software doesn't save your data, the only way to output your graph is to make a printscreen.

Based on the description (link below), the Sociogram software claims to save the data as text and allow reloading.  It also has a 'Snapshot' button that allows image export as a *.png.  

http://external.informer.com/phenotyping.com/sociogram

My experience says otherwise, but the software may have got some upgrade.

You may try the open-source Gephi, you can see some example of socigram made with him in the second link

https://gephi.org/

http://www.martingrandjean.ch/social-network-analysis-visualization-morenos-sociograms-revisited/